Data from: What doesn’t kill you might make you stronger: functional basis for variation in body armour

1. Predation has been proposed to be a selective agent in the evolution of morphological antipredator strategies in prey. Among vertebrates, one of the morphological traits that evolved multiple times is body armour, including carapaces, thickened keratinized scales and plates of dermal bone. 2. It has been generally assumed that body armour provides protection against a predatory attack; yet, few explicit tests of the hypothesis exist. Cordylidae, a relatively small family of southern African lizards, show considerable variation in the degree of body armour. Hence, this family provides an opportunity to test the hypothesis that body armour serves as protection against predators. 3. Experiments were conducted to test whether the bite forces of four species of mammalian predators were high enough to penetrate the skins of Karusasaurus polyzonus, Namazonurus peersi, Cordylus cordylus and Cordylus macropholis, as well as those of Ouroborus cataphractus individuals originating from three localities that differed in their predator diversity. Furthermore, histological techniques were used to test whether variation in skin toughness was associated with concomitant changes in the degree of epidermal (i.e. β-keratin) and dermal (i.e. osteoderm) armour. 4. The skin toughness values for four out of five cordylid lizards tested in this study were well below the bite forces of the mammalian predators. In contrast, the thick osteoderms in the dermis of O. cataphractus can withstand bites from several mongoose species. However, the significant variation in body armour that is present between the three populations of O. cataphractus does not seem to be related to predator diversity. 5. It is concluded that body armour can serve as protection against predation in O. cataphractus, but that alternative selection pressures, such as thermoregulation or predation by snakes, presumably underlie variation in defensive morphology in the other cordylid lizards.1. 捕食被认为是猎物形态学反捕食策略演化过程中的选择压力之一。在脊椎动物中，多次独立演化出的形态特征之一便是躯体装甲（body armour），包括背甲、增厚的角质鳞片以及真皮骨板。 2. 学界普遍认为躯体装甲可抵御捕食者的攻击，但针对这一假说的直接验证研究却寥寥无几。非洲南部蜥蜴类的绳蜥科（Cordylidae）是一个相对小型的类群，其成员的躯体装甲发育程度存在显著差异，因此该类群为验证"躯体装甲可抵御捕食者"这一假说提供了理想的研究模型。 3. 本研究开展了相关实验，以验证4种哺乳类捕食者的咬合力是否足以穿透以下物种的皮肤：多斑卡拉蜥（Karusasaurus polyzonus）、皮氏纳米蜥（Namazonurus peersi）、绳蜥（Cordylus cordylus）以及大鳞绳蜥（Cordylus macropholis），同时还包括来自3个捕食者多样性存在差异的种群的铠闭尾蜥（Ouroborus cataphractus）个体。此外，本研究采用组织学技术，探究皮肤韧性的变化是否与表皮（即β-角蛋白）和真皮（即骨板（osteoderm））装甲的发育程度变化存在关联。 4. 本研究测试的5种绳蜥科蜥蜴中，有4种的皮肤韧性值远低于所测试的哺乳类捕食者的咬合力。与之形成对比的是，铠闭尾蜥真皮层中厚实的骨板可抵御数种獴科动物的咬击。然而，铠闭尾蜥3个种群之间躯体装甲的显著差异，似乎与当地捕食者多样性并无关联。 5. 综上，本研究认为躯体装甲可在铠闭尾蜥中起到抵御捕食的作用，但其他绳蜥科蜥蜴的防御形态差异，其背后的选择压力可能为体温调节或蛇类捕食等其他因素。